7mm frames thickness

[The Nth Degree]

I'm designing a set of etched 0-6-0 frames and wanted to check what thickness I should be looking at.

 

Having only built wagons I'm not totally sure about the structural rigidity of various thicknesses of materials. For example, would 0.022" (0.55mm) be thick enough? I have kits with 0.7mm frames etches, but these look overly thick – but likely very sturdy.

 

On a separate point, I've noted that many kit manufacturers produce their frames in nickel-silver instead of brass – is this for the structural properties over brass?

 

At the moment I'm designing them with 0.55mm frames and half etched overlays all in brass, with two additional frame stretchers. I'm presuming this would be plenty thick and sturdy enough for a small 0-6-0.

 

Any help gratefully received.

Steve

[Sandy Harper]

I'm designing a set of etched 0-6-0 frames and wanted to check what thickness I should be looking at.

 

Having only built wagons I'm not totally sure about the structural rigidity of various thicknesses of materials. For example, would 0.022" (0.55mm) be thick enough? I have kits with 0.7mm frames etches, but these look overly thick – but likely very sturdy.

 

On a separate point, I've noted that many kit manufacturers produce their frames in nickel-silver instead of brass – is this for the structural properties over brass?

 

At the moment I'm designing them with 0.55mm frames and half etched overlays all in brass, with two additional frame stretchers. I'm presuming this would be plenty thick and sturdy enough for a small 0-6-0.

 

 

Any help gratefully received.

Steve

Hi Steve, Obviously the thicker the frames the more rigid, but that can make difficulties for those wanting to cut into the frames to fit hornblocks etc. The important measurement is the overall width between the outside faces of the axle bearings which ideally must be a fraction under the back to back measurement 0F/S. N/S is used by some manufacturers because of its inherent stiffness over brass but I am presently building the tender frames for a 2P which are etched in 0.7mm thick brass and I find them excellent. 0.55mm thick sounds a bit thin to me. Thinner brass also has a tendency to expand and warp easier with heat making it difficult to get a square chassis, especially if you are thinking of overlays as well.

 

Kind regards

Sandy

[Western Star]

Prototype frame plates varied in thickness, for example the GWR used 7/8" for small tanks and 1 1/4" for the largest tender engines...  with 1" for somewhere in-between.  What this means on 7mm is that frame plates can be between 20th and 28th for scale thickness, what you choose may depend upon wheel back-2-back and availability of material.  Some kit manufacturers use nickel silver and others use brass...  the choice of material may be influenced by which end of the price scale is the favoured ground or because the manufacturer has a desire to etch coupling rods with frame plates for hole alignment.

My preference is for nickel silver.

[The Nth Degree]

Handy info, thanks Sandy and Graham.

 

I have a pet hatred of laminating sheets together so wanted to avoid it if possible. I've found that a single sheet of 0.7mm is not very workable on my design so I've reluctantly opted for one and a half thicknesses of 0.55, but with holes on the inside of the full thickness to aid joining and not relying on only the outer edge.

 

Thanks again.

[Michael Edge]

We use .022" (.56mm) for 7mm frames, normally the whole kit is on the same thickness. This is a little underscale for most plate frames but it is strong and stiff enough in either brass or nickel silver. We use nickel silver when the loco in question had bright coupling rods and they are on the same sheet. Our industrial loco kits are all brass since they normally had painted rods. Moving to a thicker sheet means more prominent cusping and less fine detail and I don't like laminated frames either. putting the whole kit on one thickness of material keeps our costs down.

Michael Edge

Judith Edge kits

[The Nth Degree]

Thanks Michael, the points you've raised are exactly the ones I had in mnd. Another concern - coupling rods - you have answered too. Have there ever been any problems with brass rods?

[The Nth Degree]

We use .022" (.56mm) for 7mm frames, normally the whole kit is on the same thickness. This is a little underscale for most plate frames but it is strong and stiff enough in either brass or nickel silver. We use nickel silver when the loco in question had bright coupling rods and they are on the same sheet. Our industrial loco kits are all brass since they normally had painted rods. Moving to a thicker sheet means more prominent cusping and less fine detail and I don't like laminated frames either. putting the whole kit on one thickness of material keeps our costs down.

Michael Edge

Judith Edge kits

One more question, if I may: how many sheet thicknesses are your rods? My current design has them at one and a half thicknesses, so around 0.825mm – is this sturdy enough? My rough estimation is that it will be, but 0.55mm may be too thin.

[Michael Edge]

It depends on the design of the rods and the articulating system, some are now three layers, one solid in the middle, half etched each side to create thicker bosses. This is only possible with plain rods, for fluted rods an additional boss thickener is required but fluted rods are thicker than plain ones anyway. This area of kit design is always a compromise between scale dimensions and available sheet thickness but one and a half thicknesses of .022" is strong enough though.

[The Nth Degree]

Thanks Michael, much appreciated.